Redistribution of hydrogen and halogen on silanes



Unite ABSTRACT OF THE DISCLOSURE Quaternary ammonium halides and quaternary phosphoniurn halides are used as catalysts for the redistribution of silicon-bonded hydrogen and silicon-bonded chlorine or fluorine atoms in silanes. For example, methyldichlorosilane is heated with tetra-butylammonium chloride at 160 C. for 20 hours and rearranges to CH3SlC13 and CH SiClH This invention is a continuation-in-part of applicants copending application Ser. No. 429,142, filed Jan. 29, 1965, entitled, Redistribution of Hydrogen and Chlorine on Silanes, now abandoned.

This invention relates to a method of rearranging the H and chlorine or fluorine atoms in a silane of the formula (a) R SiX. in which R is a monovalent hydrocarbon radical or a monovalent halohydrocarbon radical, X is H, C1 or F and n has a value from to 3 which comprises contacting said silane (a) in which there is both SiI-I bonds and SiX bonds where X is C1 or F with (b) a catalyst of the group consisting of R' NY and R' PY in which R' is a monovalent hydrocarbon radical and Y is a halogen atom.

The redistribution reaction generally yields at least traces of the products of all possible redistribution combinations that can occur. Seldom, however, are these vari ous products present in the amounts predicted by a random redistribution of the silane hydrogen and halogen. For example, the equilibria in the chlorine-hydrogen redistributions usually favor the combinations of silanes having the most even distribution of chlorine among the silicon atoms. Thus, the following equilibrium lies far to the right With the fluorine-hydrogen system, however, the opposite is often true and the accumulation of several fluorines about a silicon atom is favored. Thus, the following equilibrium lies far to the right In many cases where the equilibria are unfavorable, e.g.:

cmnsici z cmn sicn+cH,sic1,

acceptable yields can be obtained by removing the more volatile component as it is formed.

R can be any monovalent hydrocarbon radical, e.g., alkyl radicals such as methyl, ethyl, isopropyl, sec-hexyl, Z-ethylhexyl, or octadecyl; cycloalkyl radicals such as cyclohexyl or cyclopentyl; aliphatically unsaturated radicals such as vinyl, allyl, hexenyl, cyclopentenyl, or butadienyl; or aryl-containing radicals such as phenyl, tolyl, benzyl, biphenyl, or naphthyl.

R can also be any monovalent halohydrocarbon radical, e.g., haloalkyl radicals such as 3-chloropropyl, 3,3,3- trifiuoropropyl, or 4-brom0hexyl; halocycloalkyl such as bromocyclopentyl or difiuorocyclohexyl; aliphatically unsaturated radicals such as chloroallyl or chlorocyclohex- States Pate enyl; and aryl-containing radicals such as chlorophenyl, dibromophenyl, ot,o,-trifiuorot0lyl, or bromonaphthyl.

R can be any monovalent hydrocarbon radical such as those shown for R above.

Y can be any halogen, e.g., fluorine, chlorine, bromine or iodine.

Temperature and reaction time are not critical for the process of this invention, but it is preferred to operate the reaction at a temperature of 20 to 160 C.

The concentration of catalyst is likewise not critical, but it is preferred to use from 0.1 to 5 weight percent of catalyst, based on the weight of the silane reactant.

By silane reactant it is meant the entire reaction mixture minus the catalyst. Generally the silane reactant will consist entirely of the silane or silanes to be arranged, but solvents can be added if a compatibility problem exists between two silanes to be rear-ranged, and other additives also may be desirable to enhance the reaction. .It is preferable for at least 25 weight percent of the silane reactant to consist of silanes to be rearranged.

This reaction can be used to produce hydrochlorosilanes in the following manner:

etc., where R is as defined above.

Similarly, hydrosilanes and fluorosilanes can be produced from hydrofluorosilanes by the process of this invention:

The following examples are illustrative only and Should not be construed as limiting the invention which is properly delineated in the appended claims.

EXAMPLE 1 A mixture of 0.55 ml. of methyldichlorosilane and a trace amount (a small crystal) of tetrabutylammonium chloride catalyst was sealed in a tube and heated at 160 C. for 20 hours. The tube was then cooled and analyzed by nuclear magnetic resonance spectroscopy, which indicated that the tube contained the following:

Mol percent Methyldichlorosilane -66 Methyltrichlorosilane -20 Methylchlorosilane -14 EXAMPLE 2 The experiment of Example 1 was twice repeated, substituting for the catalyst of Example 1 tetrabutylammonium bromide in one case and tetrabutylammonium iodide in the other.

The two reaction mixtures were heated for 24 hours at C. to yield in each case the same products in the same proportions as in Example 1.

EXAMPLE 3 The experiment of Example 1 was repeated, substituting tetrabutylphosphonium bromide for the catalyst of Example 1.

The reaction mixture was heated at 100 C. for 14 hours to yield the following products:

Mol percent Methyldichlorosilane -68 Methyltrichlorosilane -16 Methylchlorosilane -16 EXAMPLE 4 Two 0.55 ml. samples of trichlorosilane were catalyzed with a trace of tet-rabutylammonium chloride in one case, and a trace of tetrabutylphosphonium bromide in the other.

The samples were allowed to stand at room temperature for 24 hours to yield in both cases a mixture of trichlorosilane, dichlorosilane, and silicon tetrachloride.

When a mixture of dichlorosilane and silicon tetrachloride are reacted under the above conditions, trichlorosilane is formed.

EXAMPLE A trace of tetrabutylammonium chloride was added to 0.55 ml. of dimethylchlorosilane. This was heated at 100 C. for 16 hours to yield a mixture of dimethylchlorosilane, dimethylsilane, and dimethyldichlorosilane.

EXAMPLE 6 To 0.0015 mole each of dimethylchlorosilane and methyltrichlorosilane there was added a trace of tetrabutylammonium chloride. This mixture was allowed to stand for 11 days at room temperature to yield, by N.M.R. analysis Mol percent Dimethylchlorosilane -3 Methyltrichlorosilane -16 Methyldichlorosilane -41 Dimethyldichlorosilane -39 EXAMPLE 7 To 1 mole of dimethylchlorosilane and 1.5 moles of 3,3,3-trifiuoropropyltrichlorosilane there was added 4.4 g. of tetrabutyl ammonium chloride. This mixture was heated at 60 to 80 C. for 20 hours to give an 82 percent yield of 3,3,3-trifluoropropyldichlorosilane, along with dimethylchlorosilane, 3,3,3-trifluoropropyltrichlorosilane, and dimethyldichlorosilane.

EXAMPLE 8 EXAMPLE 9' When 0.2 mole of vinylhexyldichlorosilane and 0.1 mole of octadecyldimethylsilane are mixed with 1 weight percent of benzyldecyldimethylphosphonium chloride, based on the silane weight, and 0.3 mole of o-dichlorobenzene as a dispersing agent, and this mixture is heated at 60 C. for 20 hours, the products vinylhexylchlorosilane and octadecyldimethylchlorosilane are formed.

EXAMPLE 10 When 0.1 mole of dimethylsilane, 0.4 mole of dibromophenyltrichlorosilane, and 1 mole of xylene as a dispersing agent is heated in a bomb at 125 C. with 4 Weight percent, based on the reaction mixture weight, of 4-hexenyldiphenylmethylammonium chloride, the products dimethyldichlorosilaue, dimethylchlorosilane, dibromophenylchlorosilane, and dibromophenyldichlorosilane are formed.

EXAMPLE 11 One mole of dimethylchlorosilane and 1.25 moles of decyltrichlorosilane were heated at 60 to 80 C. for 4 days with 4.4 g. of tetrabutylammonium chloride and 8.8 grams of hexadecyloctadecyldirnethylammonium chloride to give a 45 per-cent yield of decyldichlorosilane.

EXAMPLE 12 0.3 ml. of diphenylmethylsilane and 0.18 ml. of methyltrichlorosilane were heated in a sealed tube with a trace of tetrabutylammonium chloride at 100 C. for 2 hours.

Vapor phase chromatography indicated that diphenylmethylchlorosilane and methyldichlorosilane were produced.

4 EXAMPLE 13 Phenylmethylmonofluorosilane was heated in a sealed tube at C. for 66 hours in the presence of 1% by weight tetrabutylammonium fluoride to give a mixture of 48 mol percent phenylmethyldifluorosilane and 44.7 mol percent phenylmethylsilane.

Equivalent results were obtained when 1% by weight tetrabutyl ammonium chloride was used as the catalyst.

EXAMPLE 14 1 part by weight of a mixture of phenyldimethylfluorosilane and phenylmethylsilane in a mol ratio of 2:1 were placed in a sealed tube with 0.05 part by weight tetrabutylammoniumfluoride and 0.1 part by weight benzene and the mixture was heated at 100 C. for 48 hours. The products obtained were:

Mol percent Phenyldimethylsilane 38.1 Phenyldimethylfluorosilane 35.4 Phenylmethylsilane 10.0 Phenylmethyldifluorosilane 15.5

Equivalent results were obtained when the starting silane mixture was phenyldimethylsilane and phenylmethyldifluorosilane in the molar ratio of 2: 1.

EXAMPLE 15 Phenyldifluorosilane was mixed with 1% by weight tetrabutylammoniurn chloride and heated in a sealed tube for 19 hours at 100 C. The products were:

M01 percent Phenylsilane 32.0 Phenyltrifluorosilane 60.0 Phenyldifluorosilane 8.0

Equivalent results are obtained when tetrabutylammonium fluoride was used as a catalyst.

EXAMPLE 16 A mixture of phenylsilane and phenyltrifluorosilane was used in the process of Example 15. The products obtained were:

M01 percent Phenylsilane 45.6 Phenyltrifluorosilane 47.0 Phenyldifluorosilane 7.4

in which R is selected from the group consisting of monovalent hydrocarbon and halohydrocarbon radicals,

X is selected from the group consisting of hydrogen,

chlorine and fluorine,

n is an integer of 0 to 3, comprising contacting said silane reactant in which there is both SiH bonds and SiX bonds in which X is chlorine or fluorine, with (b) a catalyst selected from the group consisting of quaternary ammonium salts of the formula R' NY and quaternary phosphonium salts of the formula R' PY, where R is a monovalent hydrocarbon radical and Y is a halogen atom.

2. The process of claim 1 where the reaction temperature is from 20 to C.

3. The process of claim 1 where from 0.1 to 5 weight percent of catalyst, based on the weight of the silane reactant, is present.

4. The process of claim 1 where the silane reactant comprises a mixture of dimethylchlorosilane and RSiCl Where R is as defined in claim 1.

5. The process of claim 1 where the silane reactant comprises a mixture of dimethylsilane and RSiC1 where R is as defined in claim 1.

6. The process of claim 1 Where the silane reactant comprises a mixture of dimethylchlorosilane and 3,3,3- trifiuoropropyltrichlorosilane.

7. The process of claim 1 where the silane reactant comprises a mixture of dimethylchlorosilane and phenyltrichlorosilane.

8. The process of claim 1 Where the silane reactant comprises a mixture of decyltrichlorosilane and dimethylchlorosilane.

9. The process of claim 1 in which the silane reactant is a mixture of methyldichlorosilane and 3,3,3-trifluoropropyltrichlorosilane.

References Cited UNITED STATES PATENTS 2,842,580 7/1958 Gilbert et a1. 260-448.2

HELEN M. MCCARTHY, Primary Examiner.

0 J. PODGORSKI, Assistant Examiner. 

